Coevolutionary dynamics shape the structure of bacteria-phage infection networks

Area of Science:

• Microbial ecology
• Evolutionary biology
• Network science

Background:

• Coevolution, the reciprocal evolutionary change between interacting species, is a key driver of biodiversity.
• Understanding coevolution's role in structuring species interaction networks is crucial for predicting community persistence.
• Microbial communities, particularly bacteria-phage interactions, offer a tractable system to study coevolutionary dynamics at ecological timescales.

Purpose of the Study:

• To experimentally investigate how different coevolutionary dynamics influence the architecture of bacteria-phage infection networks.
• To determine the extent to which coevolution drives changes in network structure, specifically nesting patterns.
• To explore the relationship between coevolutionary dynamics, infectivity, and divergence in host-parasite traits.

Main Methods:

• Experimental evolution of bacteria and phage populations under controlled conditions.
• Quantification of bacteria-phage infection networks and analysis of their structural properties, such as nesting.
• Comparison of network architecture under fluctuating versus arms race coevolutionary dynamics.

Main Results:

• Coevolving bacteria-phage interactions exhibited decreased network nesting under fluctuating dynamics and increased nesting under arms race dynamics.
• High average infectivity in coevolving systems led to greater divergence between phages and bacteria over time in arms race dynamics compared to fluctuating dynamics.
• Trade-offs between the fitness benefits and costs of evolving resistance and infectivity traits likely explain observed differences in network structure.

Conclusions:

• The specific mode of coevolution (fluctuating vs. arms race) significantly alters the structure of bacteria-phage interaction networks.
• Network architecture is not static but dynamically shaped by ongoing coevolutionary processes.
• Experimental evidence demonstrates coevolution's critical role in shaping ecological networks and influencing community properties.